ORIGINALRESEARCH Sensory evaluation of ovine milk yoghurt with inulin

addition

CELSO FASURA BALTHAZAR,* LEONARDO VARON GAZE, HUGOLEANDRO AZEVEDO DA SILVA, CAMILA SERVA PEREIRA, ROBSONMAIA FRANCO, CARLOS ADAM CONTE-J �UNIOR, MONICA QUEIROZDE FREITAS and ADRIANA CRISTINA DE OLIVEIRA SILVADepartment of Food Technology, Veterinary College, Federal Fluminense University, Rua Vital Brazil Filho 64,Niter�oi, RJ 24.230. 340, Brazil

The purpose of this study was to elaborate prebiotic yoghurt using ovine milk and different inulinconcentrations (0, 2 and 6%). Samples were submitted to laboratory analysis and two sensory testswith 100 consumers. The results of apparent viscosity and firmness determined by instrumentalanalysis of each yoghurt and control differed significantly. Just-About-Right showed consistency asthe main attribute that varied in treatments. According to penalty analysis, prebiotic yoghurt con-taining 6% inulin had minor penalties, which indicates its advantage in the quest to better con-sumer demands. Hence, this treatment demonstrated better results as well as the many prebioticbenefits associated with an adequate fibre amount.

Keywords Flavour, Prebiotics, Colour, Rheology, Texture.

INTRODUCTION

Nowadays, consumers demand healthy andunpreserved food. At the same time, the dairyindustry is concerned about developing high-nutritive products such as those enriched withprebiotics. Prebiotic use is growing in the globalmarket, and they are recognised as importantfood ingredients to keep and improve our health(Saad et al. 2013). A well-established prebioticis inulin, a soluble dietary fibre consisting of achain of fructose molecules with a terminal glu-cose molecule, which confers benefits upon hostwell-being and health (Roberfroid 2007; Guggisbertet al. 2009).According to the National Agency for Sani-

tary Vigilance of Brazil (ANVISA 2002), anintake of 1.5 g of inulin in 100 mL of liquidfood or 3.0 g per 100 g of solid food is theminimal portion necessary to assure its prebioticeffect. An inulin dose between 5 and 8 g perday should be sufficient to elicit a positive effecton the gut microbiota. However, possible sideeffects, such as intestinal discomfort from gasproduction, may occur with intakes above 20 gper day (Kolida and Gibson 2007). Nevertheless,

this nondigestible polysaccharide presents inter-esting characteristics when added to dairy prod-ucts such as yoghurt, providing nutritional andtechnological positive effects (Meyer et al.2011).Extensive studies have shown beneficial

effects of inulin intake, such as bifidogeniceffect and intestinal motility (Marteau et al.2011); stimulation of the immune system(Wendy et al. 2008; Lomax and Calder 2009);increase in calcium absorption (Lobo et al.2009); satiety enhancing with potential positiveconsequences on weight management (Parnelland Reimer 2009); and chronic diseases preven-tion, such as cancer of colon (Brighenti 2007;Rault-Nania et al. 2008; Davis and Milner2009).Moreover, inulin fibre has also interesting

technological properties such as low-caloricsweetener, bulking agent, fat substitute and tex-ture modifier (Guggisbert et al. 2009). Due toits physicochemical properties, inulin can mod-ify the texture of dairy products and may signifi-cantly influence their sensory quality (Tunglandand Meyer 2002). It was also reported, whenadded to foods at low concentrations, the

*Author forcorrespondence. E-mail:celsofasura@id.uff.br

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doi: 10.1111/1471-0307.12189

rheological properties and sensory quality of the product arenot strongly affected due to its neutral or slightly sweet fla-vour and limited effect on the viscosity (Franck 2002; Kaly-ani Nair et al. 2010).Yoghurt is among the most popular of dairy products due

to various health claims and therapeutic values (Serafeimi-dou et al. 2012). This fermented milk has traditionally beenconsidered a healthy, enjoyable and easy–to-eat product,with an attractive sensory quality (Meyer et al. 2011). Inaddition, yoghurt is a fermented dairy product with specificrheological and textural characteristics. Its texture resultsfrom the development of a three-dimensional network ofmilk proteins due to the aggregation of casein micelles withdenatured whey proteins through hydrophobic and electro-static bonds (Paseephol et al. 2008). This dairy productshows a time-dependent and shear-thinning flow behaviourand the viscoelastic response of a weak gel (Meyer et al.2011). Furthermore, nutritional value and sensory quality ofyoghurt are also influenced by milk chemical composition(Kaminarides et al. 2007).Ovine milk has high fat and solid content (Park et al.

2007; Milani and Wendorff 2011). Indeed, ovine milk isricher in fat, proteins, ash, calcium, iron, manganese, phos-phorus, zinc, medium-chain fatty acids, monounsaturatedfatty acids, linolenic acid, all essential amino acids and mostof vitamins (except for carotene) than bovine milk and cap-rine milk, as this milk is a food of high biological value andhigh digestibility, hypoallergenicity and alkalinity (Kamina-rides et al. 2007; Park et al. 2007). Thus, ovine milk and itsdairy products, from the nutritional point of view, promotesbeneficial health effects (Martini et al. 2012).To design and develop new inulin-enriched functional

foods that are acceptable to the consumer, as well as con-tributing specific health benefits, it is necessary to know towhat extent their acceptability can be influenced by themodification of their composition. The nutritional and tech-nological characteristics of inulin make it a very attractiveingredient (Villegas et al. 2010). According to Stone et al.(2012), the Just-About-Right (JAR) scale allows theresearcher to assess the level of affection of certain attri-butes which the consumer may consider optimal. More-over, penalty analysis is a statistical methodology able todetermine, for each attribute of JAR, their respective influ-ences on scores of acceptance. Many papers related theimportance of these attributes on the overall acceptability(Cavitt et al. 2005; Cadot et al. 2010). Through the effectsof mean drops, the penalty analysis allows the product tobe penalised for each attribute of JAR, being ‘not enough’and ‘too much’ for more than 20% of consumer’ respon-dents (Cadot et al. 2010; Lee et al. 2011). Lately, manysensory studies are using these tools to improve the con-sumers’ perception of tested foods such as wine (Cadotet al. 2010), wheat-germinated brown rice bread (Char-oenthaikij et al. 2010), marinated broiler breast meat (Lee

et al. 2011), nonflavoured yoghurts (Toschi et al. 2012),prebiotic low-fat milk beverages (Villegas et al. 2010) andmany others.Despite the scientific evidence related to the physiological

effects of inulin, there is a lack of literature on technologicaland sensory aspects of the optimal concentration of thiscompound when used in dairy ovine products. In this con-text, the aim of this study was to elaborate yoghurts fromovine milk containing different prebiotic inulin fibre concen-trations (0, 2 and 6% w/w), to check the influence of inulinon yoghurt consistency and to evaluate consumer responsesto this new product from acceptability and Just-About-Rightsensory tests.

MATERIAL AND METHODS

Starter culture preparationStrains of lactic acid bacteria Direct Vat Set (DVS)YF-L903 (Yo-Flex�, Chr Hansen, Valinhos, SP, Brazil)were purchased. Then, 500 mL of milk was reconstituted at16% w/w of skimmed milk powder (SMP) (Ninho�,Nestl�e�, Rio de Janeiro, RJ, Brazil) and kept at 105 °C for10 min to ensure the safety of the sample. A lyophilisedstarter culture (2.35 9 109 cfu of Streptococcus thermophilusand 1.35 9 1012 cfu Lactobacillus delbrueckii subsp.bulgaricus) was inoculated in this prepared milk. Aliquots of10 mL were obtained and frozen at �18 °C. Each aliquot ofthe prepared starter culture was thawed under refrigerationand inoculated into a litre of whole-pasteurised ovine milk.

Yoghurt productionWe purchased 20 L of whole raw milk obtained fromLacaune ewe flock located in Rio de Janeiro State mountain-ous region. At the Dairy Laboratory pilot plant. At the dairylaboratory pilot plant, the ovine milk samples (6.67 L each)were made up as follows: control yoghurt containing 0% w/wof inulin (C), Treatment 1 containing 2% w/w of inulin (T1);and Treatment 2 containing 6% w/w of inulin (T2). The pre-biotic samples (T1 and T2) were subjected to continuous agi-tation for 5 min to complete the dispersion of inulin powder.The inulin polymer (Ingredients & Systems Biotechnology,S~ao Paulo, SP, Brazil) has a degree of polymerisation from 2to 50 and an average degree of polymerisation of 9.Each batch treatment (6.67 L of ovine milk) was subjected

to heat treatment at 93 � 2 °C for 5 min in a stainless steeldouble-jacket container. Afterwards, they were cooled to43 � 2 °C in ice bath for starter culture inoculation andmixed for 5 min. The samples were put in a digital pro-grammed incubator (SP-200, SP Labor, S~ao Paulo, SP, Bra-zil) at 43 � 1 °C for 4 h. The yoghurts were stirred after thefermentation period and stored under refrigeration at4 � 1 °C for further analysis (Figure 1). The yoghurts wereproduced twice, three different treatments (C, T1 and T2) perday.

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Bacterial countsAnalyses of thermotolerant coliforms and Salmonella spp.were performed on pasteurised ovine milk and yoghurtaccording to APHA (2001). The count of Streptococcusthermophilus was performed on M17 agar (Agar M17 Base –Model M929, HiMedia Laboratories, Mumbai, India), andthe count of L. delbrueckii subsp. bulgaricus was performedon Agar de Man, Rogosa and Sharpe (MRS) (LactobacillusMRS Agar – M641, HiMedia Laboratories, Mumbai, India),according to Codex 243-2003 Stand for fermented milk(Codex Alimentarius 2010). All bacterial counts wereperformed in triplicate.

Physicochemical analysesThe following analyses were performed on the samples ofraw ovine milk: relative density, dry milk solids-not-fat, cry-oscopy (LAC 50, Boeco LAC, Hamburg, Germany), protein(AOAC 1980), fat (ISO 488/IDF 105 2008), titratable acid-ity (AOAC 1999) and pH using a digital pH meter (ModelPG1800, Cap Lab�, SP, Brazil). Titratable acidity and pHwere also determined in yoghurts. All physicochemicalanalyses were performed in triplicate.

Colour measurementColour measurement was performed on six separate determi-nations on each batch at 7 � 2 °C of day one treatmentsusing a portable chroma meter (CR-410, Konica MinoltaSensing, Inc., Tokyo, Japan). The coordinates L*, a* andb* were obtained using the CIE scale, where L* is a mea-sure of the lightness, a* varies from green (�) to red (+)and b*varies from blue (�) to yellow (+) using D65 illumi-

nant and observer at 10 °C. The whiteness index (WI) wascalculated by Vargas et al. (2008) equation:

WI ¼ 100� 100� L�ð Þ2 þ a�2 þ b�2�1=2h

Apparent viscosity analysisApparent viscosity of the treatments was determined at7 � 2 °C using rotational viscometer microprocessor(Q860M21, Quimis�, Sao Paulo, SP, Brazil) and spindlenumber 4. The spindle was rotated at 20 r.p.m. The read-ings were recorded at the 30th second of the measurementperiod as millipascal seconds (mPa.s). Five separate deter-minations were performed on each batch at 7 � 2 °C.

Compression analysisA single compression test was performed using a textureanalyzer (TA-XT plus�, Stable Micro System Ltd., Godal-ming, Waverley District, U.K.) equipped with a 5-Kg loadcell using the method of Paseephol et al. (2008). The treat-ments were compressed with a 20-mm diameter cylindricalprobe (36 R) to a depth of 10 mm at a constant speed of1 mm/s. Gel firmness was determined as the maximumforce (N) on the compression force time–curve. Four sepa-rate determinations were performed on each batch at7 � 2 °C.

Consumer sensory analysisThe tests were conducted in laboratory conditions with 100consumers randomly recruited. They were between 15 and58 years of age, with 61 females and 39 males. The samples(C, T1 and T2) were served in monadic form at 15 °C inwhite polyethylene cups, coded with three random digits.Balanced design, proposed by MacFie et al. (1989), deter-mined the order of presentation of the samples to each con-sumer. Potable water was used to clean the palate.Consumers received a scorecard to answer the tests. In

the acceptability test, appearance, smell, taste, texture andoverall impression were evaluated in a 9-point hedonic scaleranging from 1 (‘dislike extremely’) to 9 (‘like extremely’).The Just-About-Right scale scorecard had five items to beevaluated: consistency, acid taste, sweet taste, milk flavourand salty taste. In this second test was utilised a 9-pointscale ranging between 1 (‘Extremely Less’), 5 (‘Just-About-Right’) and 9 (‘Extremely More’).

Statistical analysesInstrumental and sensorial data were treated by analysis ofvariance (ANOVA), and mean separation was conducted byTukey’s test at P < 0.05 with XLSTAT version 2013.2.03(Addinsoft, Paris, France). The acceptance data weregrouped by principal component analysis (PCA), which alsoindicates the attributes of acceptance that stood out for eachtreatment. Just-About-Right scale data were treated with pen-

Figure 1 Flow chart of prebiotic yoghurt production from ovine milkwith different inulin contents. C: control yoghurt (0% w/w of inulin);T1: Treatment 1 (yoghurt containing 2% w/w of inulin); T2: Treatment 2(yoghurt containing 6% w/w of inulin).

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alty analysis, which was performed to determine, for eachattribute, whether the rankings on the JAR scale were relatedto significantly different results in the preference scores.

RESULTS AND DISCUSSION

Bacterial countsSalmonella spp was absent in 25 mL of pasteurised ovinemilk and yoghurt samples. The raw milk presented2 9 101 MPN/mL of coliform bacteria (30/35 °C) and wasnegative after heat treatment, so proving its efficacy.The yoghurt starter cultures counts for Streptococcus ther-

mophilus were 1.1 9 108, 1.3 9 108 and 1.8 9 108 cfu/mLrespectively, in samples C, T1 and T2. Similarly, counts ofL.delbrueckii subsp. bulgaricus were 1.4 9 108, 1.0 9 108

and 1.2 9 108 cfu/mL respectively, in samples C, T1 and T2.Lactic acid bacterial counts did not seem to be affected by theincorporation of inulin in yoghurts.

Physicochemical analysesSome physical properties and average composition of basicnutrients of ovine milk are shown in Table 1. Moreover,these results are in accordance with other studies (Parket al. 2007).The analytical results (Table 2) showed significant differ-

ence in titrable acidity. However, no significant alterationin pH between the treatments was observed, as alsoreported by Guggisbert et al.(2009), Mazloomi et al.(2011),Paseephol et al. (2008) and Villegas et al.(2010), and thislatter study analysed the effect of inulin in low-fat milkbeverage formulations. According to Franck (2002), pH ofchicory inulin oscillates between 5 and 7, depending onthe average degree of polymerisation. Indeed, the inulinconcentration appeared not to influence the pH level(Guven et al. 2005).

Colour measurementThe colour science seeks to link the fundamental propertiesof light and matter to human perception and the ability tocapture and generate colour relates to its importance in awide range of manufacturing industries. The colour sciencewas divided into three branches namely the colour proper-ties of the lighting (illuminant), the colour properties of theobject and the colour response of the detector or observer(Joiner et al. 2008).Regarding colour, the parameters L*, a* and b* of colour

scale allow identification of the WI of the products (Table 2).The white appearance of milk results from its physical struc-ture, influencing lightness (L*). The milk colour is also influ-enced by plasma carotenoids, such as lutein and b-carotene(a* and b*, respectively) (Nozi�ere et al. 2006).The lightness (L*) of prebiotic yoghurts (T1 and T2) was

significantly higher than in C. Apparently inulin moleculesinteracted with casein micelle, which along with the fat

globules are responsible for the diffusion of incident lightand consequently of the high L* value of this matrix(Nozi�ere et al. 2006). Differing with the present study, Ar-yana et al. (2007) did not verify difference of lightness inbovine milk yoghurts containing 1.5% w/w of inulin. Thisdifferent behaviour can be explained by the higher concen-tration of casein and fat globules in this matrix, and also thedifference of casein micelle subunit concentrations andsmaller fat globules size compared with bovine milk (Parket al. 2007) and higher inulin amount used in the study.However, Villegas et al. (2010) observed a statisticallyhigher L* value for inulin low-fat milk beverage, in agree-ment with this study.The a* value was statistically the same for the three ovine

milk yoghurt treatments (0.75; 0.74; and 0.76, respectively,for C, T1 and T2); thus, inulin did not influence this colourparameter. The a* value from all treatments were low com-pared with bovine milk (Mazloomi et al. 2011), becauseplasma carotenoids are lower in ovine milk than bovine milk(Nozi�ere et al. 2006). Although the a* value was lower thanthe same value observed in other researches (Aryana et al.2007; Villegas et al. 2010; Mazloomi et al. 2011), have had

Table 1 Average of basic nutrients composition and physicochemicalproperties of ovine milk

Composition/Properties Ovine milk

Fat (% w/w) 6.30Solids-not-fat (% w/w) 9.77Protein (% w/w) 5.00Density 1.033Freezing point (°H) -0.641Titrable Acidity (lactic acid % w/v) 0.17pH 6.86

Table 2 Physicochemical results of ovine milk yoghurt treatmentswith different inulin concentration

Physicochemical properties C T1 T2

pH 4.41a 4.39a 4.43a

Acidity (lactic acid % w/v) 0.94a 0.88b 0.84c

Lightness (L*) 96.08a 96.83b 96.13c

Whiteness Index 94.03a 93.68b 93.73b

Apparent Viscosity (mPa.s) 6626.9a 7314.1b 8528.8c

Firmness (N) 0.625a 0.732b 1.038c

Averages in the same row with different letters (a–c) differs

P < 0.05.

C: control yoghurt (0% w/w of inulin); T1: Treatment 1 (yoghurt

containing 2% w/w of inulin); T2: Treatment 2 (yoghurt containing

6% w/w of inulin).

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similar behaviour of a* value, as showed in the presentstudy, when inulin was added to the milk.Nevertheless, the b* value was higher for prebiotic

yoghurts than for the control (4.44; 5.42; and 4.88, respec-tively, for C, T1 and T2) which was indicated by a lesswhite appearance of the yoghurt. Schreiner (1950) reporteda colorimetric method for the determination of inulin bymeans of resorcinol, due to the ability of inulin to changethe medium colour after acid hydrolysis. When this reactionoccurs above 40 °C, the colour development is progressive,while at 100 °C, the reaction induces the pale yellow col-our. Acid hydrolysis can probably take place in yoghurtcontaining inulin due to the presence of lactic acid formedby the starter culture and adequate fermentation temperature(42 � 1 °C), interfering with the colour of prebioticyoghurts (T1 and T2).The inulin may also influence b* components in agreement

with Aryana et al. (2007) and Mazloomi et al. (2011), asthese authors reported slightly higher b* value in yoghurtscontaining inulin compared with their controls, althoughnonsignificant differences were found. The b* value from alltreatments was low compared with bovine milk (Mazloomiet al. 2011) and even so, ovine milk yoghurt is whiter thanbovine milk yoghurt which is devoid of b-carotene, a carot-enoid responsible for the yellow colouration (high b* value)of cattle milk (Nozi�ere et al. 2006).Moreover, the WI of T1 and T2 were significantly lower

than C, meaning a less white prebiotic yoghurt and so con-tradicting the trivial thought that the lighter something is,the whiter it appears. Although the hue that generally devi-ates from the white point is deemed to be less white thanthose of similar lightness (Joiner et al. 2008), Juan et al.(2013) reported that, due to its particle nature, inulin can actas a light-scattering centre and increase the opaqueness ofcheeses.

Apparent viscosity analysisThere was a significant increase in apparent viscosity in treat-ments with added inulin, as in T2, the most viscous in rela-tion to C and T1 (Table 2). This result was expected becauseof the capacity of inulin to retain water though the formationof small aggregates of microcrystals (Gonz�alez-Tom�as et al.2008; Soukoulis et al. 2009), and the interaction with milk

protein that can lead to an increase in the molar mass. Thisresults in increased viscosity (Schaller-Povolny and Smith2001), due to increasing total solids (Meyer et al. 2011).Similar behaviour was observed by Guggisbert et al. (2009)in yoghurt manufactured using bovine milk containing 0, 1,2 and 4% w/w inulin. In the same way, Alves et al. (2009)reported that 1% w/w inulin influenced texture characteris-tics, improving creaminess, airiness and viscosity in probioticcaprine milk frozen yoghurt. However, no reports were foundin the literature about apparent viscosity increase using fibreinulin in ovine milk yoghurt.

Compression analysisRegarding firmness (Table 2), the treatments T1 and T2 hada greater consistency than C, thus inulin was responsible forthe firmness increase. In addition, the inulin molecules dis-persed within the protein matrix develop a three-dimensionalnetwork through hydrophobic and electrostatic bonds withcasein micelles and denatured whey proteins responsible formore creamy gel formation of yoghurt and consequentlyenhancing gel stability (Paseephol et al. 2008). The behav-iour of increasing firmness associated with the inulin con-centration increases observed in this experiment is inaccordance with Guggisbert et al. (2009) and Oliveiraet al.(2009), who worked with different concentrations ofinulin ( 0, 1, 2 and 4%) in both yoghurt and fermented milkmade of bovine milk. However, no reports have been foundin the literature about firmness increase using fibre inulin inovine milk yoghurt.

Consumer sensory analysisNo significant effects of age or sex were observed on consu-mer preferences nor were any changes over time. Data fromall participants was combined for all the analyses.Table 3 shows the mean scores for the acceptability test

attributes of ovine milk yoghurt containing inulin in a scaleof acceptability, sorting the key attributes responsible forinfluencing the acceptance. The addition of different concen-trations of inulin to dairy beverages to change some physi-cal and sensory product properties was found acceptable tothe consumer. It is necessary to analyse what extent inulinaddition or the possible interaction with other ingredientsmay cause perceptible variations in the sensory features and

Table 3 Acceptance test attributes of ovine milk yoghurt treatments with different inulin concentrations

Appearance Smell Flavour Texture Overall liking

C 6.9a 6.7a 4.8a 6.4a 5.7a

T1 7.1a 6.7a 5.0ab 6.7a 5.9a

T2 6.8a 6.7a 5.3b 6.2a 5.8a

Averages in the same column with different letters (a–c) differ P < 0.05.

C: control yoghurt (0% w/w of inulin); T1: Treatment 1 (yoghurt containing 2% w/w of inulin); T2: Treatment 2 (yoghurt containing 6% w/w of

inulin).

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whether any variations affect the product acceptability(Villegas et al. 2010).There was no significant difference on appearance, smell,

texture and overall liking, demonstrating that C, T1 and T2are equal for consumers. Apparently, inulin did notinfluence some attributes of yoghurt, such as found byMazloomi et al. (2011). The same could not be verified forflavour acceptance, where consumers distinguished C fromT1 which was the first to score ‘slightly dislike’.Tungland and Meyer (2002) reported that concentrations

of inulin can increase the structure and texture acceptanceof dairy products, significantly influencing the sensory qual-ity. In addition, different levels of inulin could vary thephysicochemical and sensory properties and consumers’ per-ceived sensory differences, mainly the perception on sweet-ness and thickness of the vanilla beverages (Villegas et al.2010). However, Franck (2002) and Kalyani Nair et al.(2010) demonstrated that, when this fibre is added to foodsat low concentrations, the rheological properties and sensoryquality of the product are not strongly affected due to itsneutral or slightly sweet flavour and limited effect on theviscosity. In addition, in the case of human perception aboutthe acceptance attributes, differences between treatmentswere observed but not as it would be expected, indicatingthat the sensory perception characteristics of individuals donot classify the increase in flavour or texture linearly withinulin concentration increases.Lovely and Meullenet (2009), Cruz et al. (2012) and Desai

et al. (2013) conducted acceptance tests with samples ofbovine milk yoghurt, respectively, strawberry, probiotic andGreek. These authors evaluated and obtained similar behav-iours between the attributes, namely overall liking, appear-ance, taste and texture, using a hedonic scale of nine points.

Lovely and Meullenet (2009) studied different preferencemap methodologies and generated formulations of those whowould be considered JAR for strawberry yoghurt and per-formed acceptance test. The acceptances of theseformulations ranged as overall liking (6.4–7.0), appearance(6.6–6.8), flavour (6.4–7.0) and texture (6.4–7.2). Thus, theprebiotic ovine milk yoghurt is as acceptable to consumers asthose traditionally marketed. The consumers did not rejectthe product on the basis of the evaluation of results in theresults in their study. However, more studies about accep-tance drivers should be performed in order to better meet thedemands of consumers who are habituated to yoghurt formu-lations of bovine milk. Bayarri et al. (2010) found an overallliking ranging from 6.50 to 7.29 in three natural bovine milkyoghurts, a higher range than observed for the same attributein ovine milk yoghurt (range of 5.8) in this study.Figure 2 shows that PCA could explain 100.00% of data.

The principal component 1 (PC1) was responsible for60.26% of data explanation, whereas principal component 2(PC2) explained 39.74%. The PCA formed three groupscomposed by C, T1 and T2 (Figure 2b). It can be observedin Figure 2a that C acidity and WI were outstanding factorsdifferentiating it from the other samples, due to its higher ti-trable acidity and whiteness. Already, T1 had the mostobvious influence on most of the variables (appearance, b*,L*, overall liking, smell and texture). Lastly, T2 had someoutstanding factors (a*, apparent viscosity, firmness, pH andtaste) as relevant parameters influencing acceptability byinulin technological characteristics.Almost all parameter settings of instrumental analysis

showed significant difference (Table 2). Surprisingly, thesedifferences were not noticeable to consumers in the accept-ability test (Table 3) concerning the attributes of appear-

Appearance

Smell

Flavour

Texture

Overall Liking

L*

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Figure 2 Bidimensional projection of principal component analysis of acceptability test showing positions of quantitative variables (a) and samples(b). Different hues of grey circles mean outstanding factors of each treatment. C: control yoghurt (0% of inulin); T1: Treatment 1 (yoghurt containing2% of inulin); T2: Treatment 2 (yoghurt containing 6% of inulin).

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ance, texture and overall impression. Brennan and Tudorica(2008) observed that levels above 2% w/w of inulin wereneeded to exert significant improvements in apparent viscos-ity. The sensory analyses did not detect differences in theviscosity perceived, but incorporation of 6% w/w inulin sig-nificantly improved the creaminess, mouth feel and smooth-ness. The present study found the same results for 2% w/winulin, even though the texture acceptance of 6% w/w inulinfor consumers was not significantly different.According to Buriti et al. (2008), inulin is responsible for

apparent viscosity and firmness increase in symbioticcheese; Gokavi et al. (2005) observed a better score of sym-biotic fermented beverage containing inulin in sensoryanalysis. This behaviour is in accordance with this study,where the rheological effects of inulin were confirmed in T2and a better sensory analysis score was obtained in T1 (Fig-ure 2).Figure 3 provides the relative frequencies of the partici-

pants’ responses over C, T1 and T2, divided into three cate-gories: below JAR, JAR and above JAR. Based on this,frequencies below 20% did not provide a clear direction forproduct changes; these should not be considered when inter-preting the results (Mac Fie 2007). The attributes thatpleased most participants in all treatments were milk fla-vour, followed by consistency. However, the sweet tastewas always placed as less than JAR, due to the high mineralcontents in ovine milk (Park et al. 2007). An appreciablepercentage of consumers also indicated the salty and acidcharacteristics of the product, as these two categories rangedfrom 57 to 75% (above JAR). The effects on mean dropindicated the difference between the averages of levelsabove JAR and below JAR of acceptance for the JAR; thus,this information showed how acceptance points were lost byhaving a product above JAR or below JAR. Therefore, itcan be observed that the values ranged from 0.29 (aboveJAR, for C consistency) to 1.64 (below JAR, milk flavouralso for C). Notably, a considerable number of consumersconsidered the acid taste of prebiotic yoghurt treatmentJAR. Consistency was the main attribute that varied accord-ing to the treatments, and this attribute dropped 32–17%from C to T2 (below JAR), and raised 20–44% (aboveJAR), indicating an increase in the consistency of theyoghurt containing inulin.The 70% JAR acquisition or more represents the impor-

tance of that attribute for obtaining its ideal (Meullenetet al. 2007). Therefore, no treatment has obtained this fre-quency represented in the JAR. It is not uncommon withresults using JAR scale, as demonstrated by Lovely and Me-ullenet (2009) who also had results below JAR. Finally, itwas observed that C achieved a degree of acidity aboveJAR from the sensory point of view and the equivalent of0.94% w/v acidity was clearly perceivable by the consumer.Hence, it was demonstrated that positive inulin sensorial

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52

23

%

T2

Figure 3 Frequency distribution in percentage of consumer responsesfor Just-About-Right scores for each dimension, yoghurts containing dif-ferent concentrations of inulin. C: control yoghurt (0% of inulin); T1:Treatment 1 (yoghurt containing 2% of inulin); T2: Treatment 2 (yoghurtcontaining 6% of inulin). (-) below Just-About-Right (JAR), (.) JAR and(/) above JAR.

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interference was perceived in yoghurts with prebiotic addi-tion were less acid in the physicochemical analysis acidity.Table 4 lists the penalties, denoting the product accep-

tance points lost so that it did not meet consumer expecta-tions. The penalties of the attribute consistency did notchange much with treatments. The presence of inulinseemed to influence the acid taste, increasing the penaltiesof prebiotic yoghurts (T1 and T2). In addition, the milk fla-vour had fewer penalties in prebiotic yoghurt sensory analy-sis. It can be observed that T2 generated the fewer penaltiesin terms of sweet and salty taste attributes, which indicatesan advantage of this treatment in the quest for better con-sumer acceptance.

CONCLUSION

Soluble dietary fibre inulin did not interfere with the sen-sory attributes of ovine milk yoghurt, such as appearance,smell, texture and overall liking, and improved the flavouracceptance. Both prebiotic and nonprebiotic ovine milkyoghurts were accepted by consumers. based mainly onappearance, smell and texture. According to our study, itwas the addition of prebiotic fibre inulin in this matrix hada positive effect on the technological aspects of yoghurt.Nutritional benefits associated with inulin could bringattractive novel products to fulfil a market niche. Hence,treatment with 6% w/w of inulin demonstrated better resultsas well as the prebiotic benefits associated with animproved amount of fibre.

ACKNOWLEDGEMENTS

The authors are grateful for financial support of Fundac�~ao Car-los Chagas Filho de Amparo �a Pesquisa do Estado do Rio deJaneiro (FAPERJ), process numbers E-26/103.003/2012 andE-26/112.393/2012. The authors C. F. Balthazar, L. V. Gazeand H. L. A. Silva e C. S. Pereira were supported by the Con-selho Nacional de Desenvolvimento Cient�ıfico e Tecnol�ogico(CNPq), Universidade Federal Fluminense (UFF) and Coorde-nac�~ao de Aperfeic�oamento de Pessoal de N�ıvel Superior(CAPES), respectively. We also thank the participation of con-sumers and the N�ucleo Avanc�ado de Educac�~ao em Tecnologiade Alimentos e Gest~ao de Cooperativismo (NATA, S~ao

Gonc�alo, Brazil) for providing their Sensory Analysis Labora-tory.

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